Electric motor actuated stop and self-closing check valve

ABSTRACT

An electric motor actuated stop/check valve for industrial use such as liquid pumping systems which has a controlled opening and closing rate when liquid flow is in a forward direction but closes quickly upon reverse flow of liquid with no action from the electric motor actuator.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.10/942,062, filed Sep. 15, 2004, which is a Continuation-in-Part ofapplication Ser. No. 10/617,435, filed Jul. 11, 2003, which is aContinuation-in-Part of application Ser. No. 09/507,273, filed Feb. 18,2000. The contents of application Ser. No. 09/507,273 are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to electric motor actuated valves incorporating acheck valve feature for controlling the flow of pumped liquids inapplications such as are associated with municipal water supply orsewage treatment facilities and industry.

2. Description of Related Art

Valves for controlling liquid flow and preventing its back-flow areknown in the art and are commonly referred to as stop/check valves. Suchvalves can be actuated to control liquid flow by manual, hydraulic andother means.

U.S. Pat. No. 4,667,696 describes a stop/check valve which utilizes aball which closes upon a valve seat to prevent liquid flow in aback-flow direction. Flow in a desired direction is regulated by ahand-cranked closing device acting on the ball.

U.K. Patent specification 141,148 describes a stop/check valve for fluidhaving a pressure plate extending from a clack into a path of returnflow of the fluid so as to urge the clack to a closed position. In anembodiment having control of forward-flow, a hand-actuated spindle isused to position the clack.

U.S. Pat. No. 4,945,941 describes a stop/check valve having a featurefacilitating movement of a valve disc to a closed position withback-flow of liquid by use of a ridge on the valve seat and a deflectorring on the valve disc to deflect the flow of the fluid. Control of theliquid for forward-flow is carried out with a hand-actuated valve stem.

SUMMARY OF THE INVENTION

The present invention provides an electric motor actuated valve tocontrol liquid flow in a forward direction, prevent flow of the liquidin a reverse direction and carry out such control while eliminating orreducing liquid surge pressure transients and slamming of componentswithin the valve. A discontinuous connection between a motor actuationcomponent and valve seating components allows valve seating solely bymeans of liquid acting on the valve seating components to close thevalve and prevent liquid back-flow. Such back-flow prevention occurswithout action by the electric motor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-section of a wye valve of the invention withan actuator rod in an extended position and a valve disc in a closedposition;

FIG. 2 is a vertical cross-section of the wye valve of FIG. 1 with theactuator rod in a retracted position, the valve disc in an open positionand liquid flow in a direction from an inlet port to an outlet port;

FIG. 3 is a vertical cross-section of the wye valve of FIG. 1 with theactuator rod in a retracted position and the valve disc in a closedback-flow preventing position;

FIG. 4 is a vertical cross-section of a wye valve embodiment of theinvention having a closing speed regulator, an actuator rod in anextended position and a valve disc in a closed position;

FIG. 5 is a vertical cross-section of the wye valve of FIG. 4 with theactuator rod in a retracted position, the valve disc in an openposition, and forward liquid flow in a direction from an inlet port toan outlet port;

FIG. 6 is a vertical cross-section of the wye valve of FIG. 4 with theactuator rod in a retracted position and the valve disc in a closedback-flow preventing position;

FIG. 7 is a schematic diagram of a valve closing speed regulator of theinvention;

FIG. 8 is a vertical cross-section of an elbow valve embodiment of theinvention with the actuator rod in a retracted position and the valvedisc in an open position for forward liquid flow in a direction from aninlet port to an outlet port; and

FIG. 9 is a schematic diagram for describing a method of operating apumping system with use of a wye valve of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1, 2 and 3 show an embodiment of the invention having a wye valvebody which provides control of liquid flow when installed in-line withliquid conveying piping having a linear configuration. Wye valve 10having valve body 12 is preferably installed in-line with use of flanges14 and 16 which bolt together with matching flanges of the piping.Liquid flow is normally in the direction of arrows 18 and is referred toin this disclosure as forward-flow. In a typical application such flowwould result from action of an up-stream pump. With forward-flow in thedirection indicated by arrows 18 a port at 20 is referred to as an inletport and the remaining port at 22 is referred to as an outlet port.Intermediate such ports and substantially perpendicular to the flow ofliquid is a valve seat 24. In a preferred embodiment the seat is annularin shape, is replaceable, and is fabricated of a metallic material suchas bronze or stainless steel. The seat can be either threaded and heldin place by complimentary threads or pinned in valve body 12, which ispreferably of a metallic material such as cast iron or ductile iron.Liquid flow is controlled by interaction of valve seat 24 and a valvedisc 26 having an integral disc stem 28. In FIG. 1 valve disc 26, isdisposed in a closed position whereat it is in contact with valve seat24 so as to block the flow of liquid through the valve body. Valve disc26 in the preferred embodiment is of cast iron or steel and can befitted with a valve disc seat, 30, of a resilient material such asrubber or UHMWPE (ultra high molecular weight polyethylene) to provide amore positive seal between the valve seat and the valve disc. Such valvedisc seat 30 is preferably retained by a bronze or stainless steelfollower ring 32 attached to the valve disc with use of stainless steelscrews 34. Disc stem 28 is of stainless steel material.Clean-out/inspection ports 35 are provided in valve body 12 to view orgain access to the valve interior.

Disc stem 28 extends through a valve body cover 36 which in thepreferred embodiment is provided with a bronze bushing 38 to enablesubstantially free movement of valve disc 26 and disc stem 28 alonglongitudinal axis 40 of the disc stem.

FIG. 2 depicts valve disc 26 and stem 28 after movement to a positionreferred to as the open position whereat liquid flow from inlet port 20to outlet port 22 is enabled. Such flow position is contrasted with thevalve disc position depicted in FIG. 1 which is referred to as theclosed position.

The valve of the invention is used in-line to 1) stop flow in theforward direction, 2) control flow in the forward direction (from fullflow to a restricted flow) and 3) prevent back-flow (flow in a directionopposite to forward-flow). In the preferred embodiment valve body 12 andvalve seat 24 are dimensioned such that the net flow area is no lessthan the cross-sectional area of the piping to the inlet and outletports so as to minimize flow restriction by the valve. That is theliquid does not encounter a cross-section, perpendicular to thedirection of flow, which is of less area than the cross-sectional areaof the adjacent piping. Configuration of the valve body, valve seat andvalve disc is such that dead or non-flow cavities do not exist withinthe valve body and the valve is therefore said to be “self-cleaning”.

Operatively attached to valve body 12 is electric motor actuator 41having actuator rod 42 positioned to act on valve stem 28. Actuator rod42 is preferably attached to a threaded shaft 43 which rotates throughaction of the electric motor to move it linearly along axis 40. In eventof loss of power or inoperability of the motor the threaded shaft can beactuated manually with a hand-crank 46. Actuator rod 42 is preventedfrom rotating with the threaded shaft by an extension from the side ofthe actuator rod which extends into a slot in anti-rotation sleeve 47.Gears linking electric motor 44 and hand-crank 46 to the threaded shaftare within housing 48. A closed position of the valve as depicted inFIG. 1 is attained by action of actuator rod 42 against disc stem 28 tomove the stem and valve disc 26 along longitudinal axis 40 to provideengagement of valve seat 24 with valve disc 26. Contact of actuator rod42 with disc stem 28 when in such closed position prevents an upwardmovement of disc stem 28 and valve disc 26 away from valve seat 24 whichwould result from pressure exerted on face 50 of valve disc 26 by liquidflowing in the direction indicated by arrows 18. Such actuator rod 42position against disc stem 28 also prevents back flow of liquid in adirection opposite to that indicated by arrows 18.

FIG. 2 shows the position of valve 10 components when full flow ofliquid in the forward direction is desired. Actuator rod 42 is at aretracted position by action of threaded shaft 43 rotated by electricmotor 44. Once the actuator rod is retracted valve disc 26 and disc stem28 move in an upward direction along longitudinal axis 40 to positionvalve disc 26 to be spaced from valve seat 24 by sole action of theliquid flowing in the direction of arrows 18 and exerting pressure onface 50 of valve disc 26. Actuator rod 42 is not connected to disc stem28 and such lack of connection is an important feature of the inventionand is relied on for prevention of back-flow of liquid which isdescribed below. Although not shown, liquid flow can be regulated toselected rates by positioning valve disc 26 between extreme positionsdepicted in FIGS. 1 and 2, however the valve is not normally used forsuch function.

As described above, the electric motor actuated stop and self-closingcheck valve of the invention can be used in municipal water supplysystems or sewage treatment systems as a pump control and stop checkvalve although it is not limited to such usage. In normal operationliquid flow is in the direction indicated by arrows 18 with such flowprovided by action of at least one pump upstream of the valve. In eventof pump shutdown, either intended or by a power failure, back-flow ofthe liquid can occur when a valve to check such flow is not provided.Such back-flow is usually undesirable and is prevented by the valve ofthe invention without any action by the electric motor. Such feature isof importance when back-flow is caused by a power failure and power isnot available to the electric motor.

In FIG. 3 such back-flow direction is indicated by arrow 52 and is in adirection from outlet port 22 toward inlet port 20. In event of a pumpshutdown liquid pressure provided by the pump and acting on face 50 ofvalve disc 26 would no longer be present and valve disc 26 would be freeto move in a downward direction so as to cover valve seat 24 and preventthe back-flow of liquid. Such downward movement of the valve disc occursby force of gravity acting on the freely moveable valve disc and discstem and also by a momentary back-flow of liquid which results inpressure being greater on back face 51 than on front face 50 of valvedisc 26. Such pressure difference closes and holds the valve discagainst valve seat 24 until such pressure difference is reversed, suchas by restarting of the pump. Such free movement along disc stemlongitudinal axis 40 can take place because of the lack of connectionbetween disc stem 28 and actuator rod 42.

A common problem with many check valves when a reversal of liquid flowdirection occurs is “slamming” of the valve disc against the valve seat.Such slamming is greatly reduced in the valve of this invention by useof a compression spring 52 which biases the valve disc and its stemtoward the closed position. Selection of spring characteristics isdependent on pressure of the liquid being pumped against valve disc face50. The spring is selected to be strong enough to assist in closing thevalve when flow in the forward direction stops so that the valve is atleast partially closed when the back-flowing liquid applies pressure tovalve disc back face 51 and any slamming of the valve disc is reduced oreliminated because of the shortened distance it moves. The spring cannot be so strong as to restrict flow in the forward direction in asignificant amount. Spring 52 is shown in a partially compressed statein FIG. 2, and in an extended state in FIGS. 1 and 3.

FIGS. 4-6 show a second embodiment of a wye valve of the invention whichincludes a second component, in addition to the spring, to reduce oreliminate valve disc slamming. Wye valve 54 of FIGS. 4-6 withforward-flow indicated by arrows 56, is similar to valve 10 of FIGS.1-3, with the exception of an added hydraulic closing-speed regulatorindicated generally at 58. Such regulator consists of piston 60 attachedto an upper end of disc stem 62, cylinder sleeve 66, solenoid valve 70,check/needle valve 72, hydraulic oil 74, hydraulic oil reservoir 76, andassociated piping. Piston 60 is free to move linearly along axis 68 incylinder sleeve 66 with movement of valve disc 64. The hydraulicclosing-speed regulator operates so as to slow down valve closing duringa reversal of liquid flow direction with substantially no effect onvalve opening speed. The hydraulic circuit of the closing-speedregulator is shown in schematic form in FIG. 7. Shown are piston 60,cylinder 66, solenoid valve 70, check/needle valve 72, hydraulic oilreservoir 76 and hydraulic oil 74. Solenoid valve 70 is open whenenergized and closes when not energized. Referring to FIGS. 4-7, whenvalve disc 64 is “opening” with movement in the direction indicated byarrow 78 (FIG. 7), flow of hydraulic oil is in the direction indicatedby arrow 80. When valve disc 64 is “closing” piston 60 moves in thedirection indicated by arrow 79 and hydraulic oil flow is in thedirection indicated by arrow 82. During planned opening and closing,when loss of power is not a factor, and slamming of valve disc 64 is nota factor, solenoid valve 70 is energized and open so as to not requireliquid flow through check/needle valve 72 (although a small flow canoccur), and operational speed of the valve being operated by theelectric motor is not affected.

During loss of power, when liquid flow is no longer in the direction ofarrows 56 and back-flow is beginning in the direction of arrow 78 (FIG.6), liquid pressure against back face 80 of valve disc 64 could, withoutclosing-speed regulator 58, slam valve disc 64 against valve seat 82. Toeliminate such slamming solenoid valve 70 closes upon loss of powerrequiring flow of hydraulic oil through check/needle valve 72 in thedirection indicated by arrow 82. Valve 72 has two channels in parallelas best seen in FIG. 7. One channel includes needle valve 84 whichadjustably controls hydraulic oil flow rate and the remaining channelincludes check valve 86 which permits flow only in the downwarddirection (as when valve disc is opening). During valve disc closing,caused by liquid back-flow, hydraulic oil flow is in the directionindicated by arrow 82 and the hydraulic oil is forced to flow throughthe restricted channel of needle valve 84 at a controlled rate, thusslowing the movement of valve disc 64 against valve seat 82 andeliminating slamming. Such rate of closing is regulated by adjustment ofthe needle valve opening.

FIG. 8 shows another embodiment of the invention, an elbow valve 86 foruse in a liquid conveying pipeline wherein a 90° pipeline configurationis available for placement of a valve. Normal liquid flow in a forwarddirection is indicated by arrows 88. During normal operation, liquidflows from entry port 90 to outlet port 92 through valve seat 94. As inthe wye valve of FIGS. 1-6 valve closure is carried out by movement ofactuator rod 96 downward by action of electric motor 98 to contact discstem 100 to dispose valve disc 102 to cover valve seat 94 and achieve aclosed position. Elbow valve 98 of FIG. 8 is depicted in the openposition wherein valve disc 102 is spaced from valve seat 94. Operationof elbow valve 98 is the same as wye valve 10 (FIGS. 1-6). The valvedisc position depicted in FIG. 8 is maintained by pressure of the liquidacting against face 104 of valve disc 102. In the event of flow stoppagein the direction indicated by arrows 88, back-flow of liquid isprevented by the action of gravity and spring 105 on freely moveablevalve disc 102 and disc stem 100, and momentary action of theback-flowing liquid on back-face 106 of valve disc 102 to move such discdownward to contact valve seat 94 and terminate the back-flow. Continuedpressure on back face (106) maintains the valve in the back-flowpreventing position.

Although elbow valve 88 with solely spring means 105 for reducing oreliminating valve disc slamming is shown, such elbow valve can beprovided with hydraulic closing speed regulating means as shown anddescribed for wye valve 10 (FIGS. 4-6) and operation of the two types ofvalves is the same.

A preferred method of operating a liquid pumping system utilizing avalve of the invention is schematically shown in FIG. 9. The system canbe used in applications such as a municipal water supply system or asewage treatment system. In FIG. 9 tank 108 is filled with liquid 110 bymeans of pump 112 acting on it. Pump input line 114 supplies the liquidto pump 112 and it is discharged through pump discharge line 116 towardliquid tank 108. An electric motor actuated stop and self-closing checkvalve 10 of the invention having a wye configured body is installed tofunction as a pump control and stop check valve in liquid discharge line116. A common problem in water and sewage systems utilizing such apumping arrangement is liquid surge pressure transients and slamming ofcheck valve components during pumping start-up and termination. Suchproblem is substantially eliminated with use of valve 10 in liquiddischarge line 116. In the preferred method of operation for pumpingstart-up, valve 10 is set to the closed position (FIG. 1) prior tostart-up of pump 112. That is actuator rod 42 is extended to locate andhold valve disc 26 against valve seat 24. The pump is then startedfollowed by opening of valve 10 toward the flow position (FIG. 2) at aselected rate with use of electric motor 41. Such rate is controllableby motor control devices known in the art (not shown). Full flowposition (FIG. 2) is maintained during normal pumping operation. Toachieve planned pumping shutdown without generating liquid surgepressure transients or valve component slamming, valve 10 is closed, ornearly closed, with use of electric motor 41 prior to shut-down of pump112. Following complete closure of the valve, or at a point nearingcomplete valve closure, the pump is switched off. Such sequentialstart-up and shut-down procedure can be conveniently controlled with useof switches and controls which coordinate the operation of the valve andthe pump.

During normal pumping operation of the pumping system with flow ofliquid in the direction of arrow 113, and actuator rod 42 in theretracted position (FIGS. 2 and 3) valve disc 26 is free to move in thedirection toward valve seat 24 and close the valve to prevent back-flowof the liquid in the event of failure of pump 112 or loss of electricalpower. No action is required by the electric motor for such back-flowpreventing closing as the valve is closed by action of the liquidflowing in a direction opposite to the direction of arrow 113. Spring 52at least partially moves valve disc 26 toward the closed position duringmomentary liquid flow reversal from forward-flow to back-flow and valvedisc slamming is eliminated or reduced. Such configuration and operatingprocedure for the pumping system enables conveying of liquid withoutundesirable liquid surging and slamming.

While specific materials and configurations have been set forth forpurposes of describing embodiments of the invention, variousmodifications can be resorted to, in light of the above teachings,without departing from applicants' novel contributions; therefore indetermining the scope of the present invention reference shall be madeto the appended claims.

1. An electric motor actuated stop and self-closing check valve forcontrolling forward and back-flow of liquid in a liquid conveying lineand reducing liquid surge pressure transients and slamming of valvecomponents, comprising: A) a valve body having an inlet port and anoutlet port, relative to forward-flow of a liquid, B) a valve seatdisposed within the valve body intermediate said ports, C) a valve discdisposed within the valve body having an elongated disc stem whichextends through the valve body, said valve disc and disc stem being freeto move along the longitudinal axis of said valve stem to either: i) aclosed position whereat the valve disc sealingly engages the valve seatto prevent forward and back-flow of the liquid, or ii) an open positionwhereat the valve disc is spaced from the valve seat, D) an electricmotor operationally attached to said valve body, E) an actuator rodmoveable by action of the electric motor to be disposed at either: i) anextended position whereat the actuator rod contacts the valve stem andrestrains the valve disc at the closed position preventing forward andback-flow of the liquid, or ii) a retracted position whereat theactuator rod is retracted and the valve disc is free to move along thelongitudinal axis of the valve stem, without action by the electricmotor, such that: a) the valve disc moves to the open position solelythrough action of forward flowing liquid on the valve disc and forwardflow of the liquid occurs, and b) the valve disc moves to the closedposition through action of momentary back-flowing liquid on the valvedisc and said liquid back-flow is prevented.
 2. An electric motoractuated stop and self-closing check valve according to claim 1, furthercomprising a compression spring biasing the valve disc toward the closedposition to move the valve disc toward the closed position followingstoppage of liquid flow in the forward direction.
 3. An electric motoractuated stop and self-closing check valve according to claim 1, furthercomprising a hydraulically operated valve disc closing-speed regulatoroperatively attached to the valve to control the closing speed of thevalve disc.
 4. An electric motor actuated stop and self-closing checkvalve according to claim 3, wherein said closing-speed regulatorcomprises, a cylinder operatively attached to the valve body, a pistonoperatively attached to the disc stem for movement within said cylinderalong its longitudinal axis, a hydraulic oil reservoir with connectingpiping to the cylinder, said connecting piping having a check/needlevalve.
 5. An electric motor actuated stop and self-closing check valveaccording to claim 1, wherein said valve body has a wye configuration oran elbow configuration.
 6. An electric motor actuated stop andself-closing check valve according to claim 1, wherein net flow area ofthe valve is no less than the cross-sectional area of the liquidconveying line and the valve is self cleaning.
 7. An electric motoractuated stop and self-closing check valve according to claim 1, whereinthe valve body is of cast iron.
 8. An electric motor actuated stop andself-closing check valve according to claim 1, further including aflange on the inlet port and a flange on the outlet port of the valvebody.
 9. An electric motor actuated stop and self-closing check valveaccording to claim 1, wherein said valve seat is replaceable and isfabricated of bronze or stainless steel.
 10. An electric motor actuatedstop and self-closing check valve according to claim 1, furtherincluding at least one clean-out/inspection port disposed in the valvebody.
 11. An electric motor actuated stop and self-closing check valveaccording to claim 1, wherein said valve disc is of cast iron or steel.12. An electric motor actuated stop and self-closing check valveaccording to claim 1, further comprising a renewable resilient seat onsaid valve disc.
 13. An electric motor actuated stop and self-closingcheck valve according to claim 12, wherein said renewable resilient seatis of rubber or UHMWPE (ultra high molecular weight polyethylene). 14.An electric motor actuated stop and self-closing check valve accordingto claim 12, further comprising a follower ring for retaining therenewable resilient seat.
 15. An electric motor actuated stop andself-closing check valve according to claim 14, wherein said followerring is of bronze or stainless steel.
 16. An electric motor actuatedstop and self-closing check valve according to claim 1, wherein saidvalve stem is of stainless steel.
 17. An electric motor actuated stopand self-closing check valve according to claim 1, further including abushing disposed between the disc stem and the valve body for guidingand facilitating the free movement of the valve disc and disc stem alongthe longitudinal axis of the disc stem.
 18. An electric motor actuatedstop and self-closing check valve for controlling forward and back-flowof liquid in a liquid conveying line and reducing liquid surge pressuretransients and slamming of valve components, comprising: A) a valve bodyhaving an inlet port and an outlet port, relative to forward-flow of aliquid, B) a valve seat disposed within the valve body intermediate saidports, C) a valve disc disposed within the valve body having anelongated disc stem which extends through the valve body, said valvedisc and disc stem being free to move along the longitudinal axis ofsaid disc stem to either: i) a closed position whereat the valve discsealingly engages the valve seat to prevent forward and back-flow of theliquid, or ii) an open position whereat the valve disc is spaced fromthe valve seat, D) an electric motor operationally attached to saidvalve body, E) an actuator rod moveable by action of the electric motorto be disposed at either: i) an extended position whereat the actuatorrod contacts the valve stem and restrains the valve disc at the closedposition to prevent forward and back-flow of the liquid, or ii) aretracted position whereat the actuator rod is retracted and the valvedisc is free to move along the longitudinal axis of the valve stem,without action by the electric motor, such that: a) the valve disc movesto the open position solely through action of forward flowing liquid onthe valve disc and forward flow of the liquid occurs, or b) the valvedisc moves to the closed position through action of momentaryback-flowing liquid on the valve disc and such liquid back-flow isprevented, F) a compression spring biasing the valve disc toward theseated position to move the valve disc toward the closed positionfollowing stoppage of liquid flow in the forward direction, and G) ahydraulically operated valve disc closing-speed regulator.
 19. A methodof operating a liquid pumping system, having at least one pump and apump liquid-discharge line, to control forward and back-flow of liquidand reduce slamming of valve components and liquid surge pressuretransients, comprising providing an electric motor actuated stop andself-closing check valve in the liquid-discharge line, comprising: A) avalve body having an inlet port and an outlet port, relative to forwardflow of a liquid, B) a valve seat disposed within the valve bodyintermediate said ports, C) a valve disc disposed within the valve bodyhaving an elongated disc stem which extends through the valve body, saidvalve disc and disc stem being free to move along the longitudinal axisof said valve stem to either: i) a closed position whereat the valvedisc sealingly engages the valve seat to prevent forward-flow andback-flow of the liquid, or ii) an open position whereat the valve discis spaced from the valve seat, D) an electric motor operationallyattached to said valve body, E) an actuator rod moveable by action ofthe electric motor to be disposed at either: i) an extended positionwhereat the actuator rod contacts the valve stem and restrains the valvedisc at the closed position preventing forward and back-flow of theliquid, or ii) a retracted position whereat the actuator rod isretracted and the valve disc is free to move along the longitudinal axisof the valve stem, without action by the electric motor, such that: a)the valve disc moves to the open position solely through action offorward flowing liquid on the valve disc and forward-flow of the liquidoccurs, and b) the valve disc moves to the closed position throughaction of momentary back-flowing liquid on the valve disc and saidliquid back-flow is prevented; then, when forward flow pumping isdesired: extending the actuator rod to its extended position, with useof the electric motor, to contact the valve stem and restrain the valvedisc at the closed position; then starting the pump to provide forpotential flow of the liquid in the forward flow direction of the valve;then retracting the actuator rod at a selected rate to the retractedposition to enable forward flow of the liquid; and when termination ofliquid flow in the forward direction is desired: extending the actuatorrod at a selected rate toward the extended position, with use of theelectric motor, so as to move the valve disc toward the closed position,then, when the valve disc is at a selected position at or near theclosed position, stopping the pump, and if the valve is not in theclosed position continuing to extend the actuator rod to position thevalve disc on the valve seat.